F134a is one of the hydrofluorocarbons (HFC) falling within the context of the replacement of the chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFC) which have already been banned or are in the process of being banned because of their harmful effect on the stratospheric ozone layer.
Several ways of obtaining F134a are known, namely:
the fluorination of 1-chloro-2,2,2-tri-fluoroethane (F133a) in gas or liquid phase; PA1 the fluorination of trichloroethylene in liquid phase; PA1 the hydrogenolysis of 1,1-dichloro-1,2,2,2-tetrafluoroethane (F114a) or of 1-chloro-1,2,2,2-tetrafluoroethane (F124); PA1 the isomerization of 1,1,2,2-tetrafluoroethane (F134).
According to the literature, the latter process is carried out using catalysts. Thus, Patents EP 365,296 and JP 03 261731 describe the use of chromium-based catalysts and U.S. Pat. No. 4,902,838 claims a catalyst of the fluorinated alumina type; Patent JP 02 115135 prefers to use a catalyst of the aluminium chlorofluoride type. The use of a catalyst is not always sufficient; thus, U.S. Pat. No. 4,902,838 recommends introducing oxygen into the medium so as to maintain the catalytic activity over time and Patent Application WO 95/15300 recommends introducing a source of chloride ions.